Ai 4 Dr. Crawford’s Experiments on the Matter 
ftate of volatile vitriolic acid, which was transferred together 
with the phlogifticated and marine acid air into the fecond 
tube ; but the greater part of the vitriolic acid produced by the 
combuftion adhered, in a fixed ftate, to the furface of the 
tube in which the airs were fired ; and therefore, when th« 
diftilled water was immediately introduced into this tube, a 
copious precipitate was depofited upon the addition of munated 
barytes. 
Hence it appears, that when pure air and fulphureous he- 
patic air, obtained from artificial pyrites by the marine acid, 
are fired together in the above proportions, the produfts are 
fixed vitriolic acid, together with a fmall quantity of the vola- 
tile vitriolic, and marine acids, in an aerial form. The refi- 
due, which the diftilled water did not abforb, was the phlo- 
gifticated air that exifted in the pure air previoufly to the 
combuftion. 
From fublequent trials it appeared, that, when hepatic and 
pure air were fired in equal bulks, the refidue had a ftrong 
odour of volatile vitriolic acid, and moreover contained a fmall 
proportion of undecompofed hepatic air. Thefe fafts feem to 
prove, that the converfion of fulphur into volatile or fixed 
vitriolic acid depends upon the quantity of pure air with which 
it is fupplied. 
The marine acid air, found in this experiment, did not 
appear to form one of the conftituent principles of tne hepatic 
air, but to be merely diffufed through it ; for it was almoft 
wholly feparated, by means of diftilled water, from a different 
portion of the fame air, which was placed in a tube inverted 
over mercury ; the water having a ftronger attraftion to the 
marine acid than to the hepatic air. 
By the following experiment I endeavoured to determine 
whether 
